This invention relates to a somewhat usual latch construction having a unique form of helical backset adjustment therein and more particularly, to such a latch construction having the helical backset adjustment which is of a maximum simplicity and form, and which operates in an extremely simple manner without any fear of error. Furthermore, the latch construction having the unique form of helical basket adjustment therein may be formed of usual materials with only slight increases in cost. Thus, an improved, adjustable latch construction is provided which perfectly serves the intended purposes in an efficient manner not possible with the prior construction.
In the various latch constructions of the type used with doors and the like, the backset measurement thereof is that distance between the forward extremities of the stationary casing longitudinally rearwardly to the transverse axis about which the latch operator moves for extending and retracting the bolt of the latch construction. These measurements have, in most modern latch constructions, been standardized by the industry. With this standardization, it is known that when a latch construction is purchased, the backset measurement will be a standard amount and from a practical standpoint, this measurement will be calculated from the forward exposed surface of the latch mounting plate which, in effect, is the forward extremity of the stationary frame or casing. Again, in a usual installation, the face plate forming the forward part of the casing is recessed in the door edge with the front surface of the face plate aligned with the door edge. Thus, in most cases, the backset measurement is also the distance from the door edge to the axis of the latch operator.
In modern industry, the most prevalent backset has been standardized at two and three eights inches so that it has normally been known prior to latch construction installation what the backset measurement would be. This premits standardized original installation and a high degree of interchangeability between various latch constructions. It is true that there have been a few "special" latch constructions having "special" backset measurements, but these have always been considered different and of no overall consequences, except requiring individual considerations for proper installation. However, more recently, a higher and higher percentage of latch constructions are being produced with greater backset measurement for various reasons including the provision of greater longitudinal length to gain increased bolt throw, that is, the longitudinal distance that the bolt is moved between retracted and extended position, in order to, in turn, provide increased security.
In view of this intended increased security, and increased backset measurement standard has now been adopted by the industry. This second standard being two and three quarters inches, three eights inches greater than the previous common standard backset. In most cases, the average manufacturer of latch constructions has satisfied this new demand for the alternate two backset measurements by producing and marketing two different and distinct models of any of the latch constructions. The one model has a backset measurement of two and three eights inches to satisfy the demand for the old standard backset, while the other model has the new standard backset of two and three quarters inches, all of which is relatively costly in view of the need for manufacturing multiple models.
Thus, there became a distinct want and need in the industry for single models of latch constructions which are relatively quickly and easily selectively adjustable between the two standard backset measurements, that is, between two and three eights inches and two and three quarters inches. Furthermore, such adjustability must be of a relatively simple nature for performance of the backset adjustment quickly and easily by relatively unskilled workmen. Various of the manufacturers have produced such single models of latch constructions which satisfy the backset adjustment feature, but none of such constructions have been of a satisfactory nature. For this reason, this distinct want and need in the industry for such a construction has persisted not only for such a construction which operates satisfactorily to carry out its required adjustment, but also one which is ralatively economical to produce.